Television is certainly one of the most influential forces of our time. Through the device called a television set or TV, viewers are able to receive news, sports, entertainment, information, and commercials. A few events stand out as extremely important in the history of television. The invention of the black-and-white TV set and the first broadcasts of television signals in 1939 and 1940 initiated the television age. This was followed by color television and its huge popularity starting in the 1950s. Cable and satellite television began competing with broadcast networks in the 1970s. In this same list must go the development and popularization of the VCR (video cassette recorder) starting in the 1970s and 1980s.
The VCR marks one of the most important events in the history of television because, for the first time, the VCR gave the viewers control of what they could watch on their TV sets and at what time. The VCR spawned the video rental and sales market, and today, VCRs are commonplace.
Now, a new innovation makes recording television programs even more convenient: the digital video recorder, or DVR. The television signal comes into the digital video recorder's built-in tuner through antenna, cable, or satellite. If the signal comes from an analog antenna or cable, it goes into an encoder, which converts the data from analog to digital form. From the encoder, the signal is sent to two different places: first, to an internal hard drive for storage, and second, to a decoder, which converts the signal back to analog and sends it to the television for viewing. For a satellite signal and for cable and antenna signals that are already digital, the encoder is not necessary.
Although the digital video recorder performs much the same functions as a VCR, there are some important differences. First, a digital video recorder is tape-less and has no removable media. With a VCR, the device itself is merely a recording tool; the blank cassette is the removable media. In a digital video recorder, the media and tool are one and the same. This is an advantage because buying and cataloging tapes are unnecessary, but it can also be a disadvantage: since the media is hard-wired internal to the digital video recorder, adding additional storage space is not always possible. Obtaining more recording time is easy with a VCR because the user need only buy another box of blank tapes, which are inexpensive and readily available. In contrast, obtaining additional recording time on a digital video recorder involves buying an entire new machine or purchasing new hardware.
Because recording time on the digital video recorder's internal hard drive is limited, digital video recorders typically cycle through the recorded programs, looking for programs to delete in order to free up space for new recordings. Digital video recorders typically have priority-based rules for selecting which programs to delete. For example, programs that the digital video recorder records automatically based on viewing habits of the user may be deleted first, followed by programs that the user has given low priority. Although deleting programs has the advantage that space is made available for new recordings, it has a significant disadvantage: programs are deleted that a user may want to view or share with others. Further, deleting programs is an all-or-nothing technique, and the user does not have the power to request automatic deleting of only a portion of a program (e.g., unwanted material or objectionable material unsuitable for certain audiences) while keeping other portions of a program that are of interest. Examples of unwanted material may be commercials or items of personal preference, such as the sports but not the weather forecast in a news broadcast.
Without a better way for managing the storage space used by programs, viewers will not be able to take full advantage of all the potential power of a digital video recorder. Although the aforementioned problems have been described in the context of a digital video recorder, they may apply to any electronic device that stores data in a limited storage space.